1. Field of the Invention
The present invention relates to a nanowire in which fine particles have been formed in a self-organizing manner on the surface of a nanowire body.
2. Description of the Related Art
Researches and developments have been carried on extensively in order to reduce the feature sizes of transistors for large-scale integrated circuits (LSIs) or thin-film transistors (TFTs) for flat-panel displays. In a silicon semiconductor process, fine line patterning with a design rule of 0.1 μm or less is realized by shortening the wavelength of an exposing radiation source for a photolithographic process. However, according to the conventional photolithography technology, the feature size cannot be reduced unlimitedly. Also, as the feature size has been reduced, the costs of exposure systems and masking members have been rising steeply.
Meanwhile, carbon nanotubes (see Non-Patent Document No. 1) and nanowires made of a material with semiconductor type properties (see Patent Document No. 1) have attracted a lot of attention recently. Carbon nanotubes and nanowires are very small structures with a diameter of about 1 nm to about 1 μm and can be formed in a self-organizing manner. That is why with those carbon nanotubes or nanowires, a high-performance electronic device of a nanometer scale could be realized even without adopting those advanced photolithography or etching technologies. For that reason, those nanostructures are expected to contribute to manufacturing high-performance devices at a reduced cost without resorting to those complicated process technologies.
Hereinafter, a conventional nanowire structure will be described with reference to FIG. 20.
FIG. 20(a) schematically illustrates the structure of a nanowire. This nanowire has a length of about 500 nm to about 1 mm, which may be appropriately determined according to its application.
FIG. 20(b) shows a nanowire 201, of which the core portion 202 (as the inner portion) and the shell portion 203 (as the outer portion) are made of mutually different materials (see Patent Document No. 2). Such a nanowire will be referred to herein as a “core-shell nanowire”.
FIG. 20(c) shows a nanowire 204 in which first and second semiconductor nanowires 205 and 206 are arranged in its length direction (see Patent Document No. 2). Such a nanowire will be referred to herein as a “hetero-nanowire”.
According to a normal heterogrowth technology that involves an epitaxy process, the lattice constants need to match at the heterojunction in order to reduce defects and dislocations, and therefore, the types of materials available are limited. However, a nanowire with a pseudo-one-dimensional structure could relax the stress that would be caused due to a mismatch of lattice constants, thus allowing for a more flexible selection of materials.
As described above, those nanowires that could realize nanostructures or material engineering in a self-organizing manner are widely expected as promising materials.
Non-Patent Document No. 2 reports that by doping a silicon nanowire with boron, the outside diameter of the nanowire can be increased and its surface comes to get rugged and have gold-rich fine particles thereon (which are called “nanoparticles”).                Patent Document No. 1: Japanese Translation of PCT International Application No. 2004-535066        Patent Document No. 2: Japanese Translation of PCT International Application No. 2004-532133        Non-Patent Document No. 1: R. Martel, et. al., “Single- and Multi-Wall Carbon Nanotube Field-Effect Transistors”, Appl. Phys. Lett. 73p, p. 2447, 1998        Non-Patent Document No. 2: L. Pan, et al., “Effect of Diborane on the Microstructure of Boron-Doped Silicon Nanowires”, J. Cryst. Growth 277, p. 428, 2005        
Nanowires have been researched extensively recently as prospective materials for use in various applications. However, since nanowires are extremely fine structures, it is very difficult to increase their functions by performing further fine-line patterning on the surface of the nanowires.
Non-Patent Document No. 1 discloses that if a nanowire being grown is doped with a dopant, the resultant nanowire will have irregular ruggedness. However, the formation of such ruggedness is non-controllable and is hard to apply to electronic devices.
It is known that a great many fine particles could be formed on the surface of a nanowire depending on the growth conditions of the nanowire. But a technique for selectively forming such fine particles on a desired region of a nanowire is not known yet. If the formation and distribution of those fine particles on the surface of a nanowire could be controlled, then a nanowire with fine particles should be applicable to various electronic devices. Unfortunately, though, nobody has ever developed such a control technique yet as of today.
In order to overcome the problems described above, the present invention has an object of providing a nanowire in which fine particles have been formed in a self-organizing manner on the surface of a nanowire body, a device including such nanowires, and a method of making such a nanowire.